Monkeypox virus is an orthopoxvirus that causes a disease with symptoms similar to smallpox in humans and other primates. It primarily occurs in Central and West Africa in proximity to tropical rainforests. There are two distinct genetic clades - the Central African (Congo Basin) clade which historically causes more severe disease, and the West African clade. Various species of rodents and non-human primates serve as natural hosts. While its natural history is still uncertain, monkeypox was first identified in humans in 1970 in the Democratic Republic of Congo and has since been reported in several other Central and West African countries.